In general, artificial snow-making involves atomizing a spray of water with a jet of air to create a plume of very fine water droplets which nucleate and form snow as the plume drops to earth under freezing temperature conditions.
The present invention is a modification of a known snow-making system patented and commercialized by Herman K. Dupre.
In U.S. Pat. No. 3,706,414, issued Dec. 19, 1972, Dupre taught bringing pressurized air and water through separate flowlines to the bases of hillside towers positioned along a ski trail. The air and water were introduced at controlled rates into a mixing chamber positioned at the foot of each tower. The mixture then flowed upwardly through a conduit forming the tower and was discharged through nozzles. Inherent in this system were the following features:
some atomization or reduction in water droplet size due to mixing with air; PA1 rapid cooling of the water when the pressurized air was released into the freezing atmosphere and it expanded; PA1 the provision of dwell time as the plume fell to earth from an elevated starting point; and PA1 some control over the air/water ratio, with a view to optimizing it. PA1 bringing the air and water through separate conduits to the discharge elevation; PA1 using the water stream to insulate the air stream until it was discharged to the atmosphere; PA1 associating the air orifice and water nozzle in a spatial arrangement such that the air jet would converge with and contact the central portion or throat of the water spray, to cause atomization; and PA1 utilizing a bank of air and water outlets. PA1 a snow gun is mounted on a boom or tower having universal movement; PA1 the gun has two banks of V-jet water nozzles spaced along the long axis of the gun; PA1 a single bank of air orifices is associated with the outer water bank; PA1 the inner bank of water nozzles directs its sprays into the nucleated sprays of the outer bank; and PA1 coaxial water and air conduits form the body of the gun and provide an annular outer passageway for supplying pressurized water to the two banks of water nozzles and an insulated inner passageway for supplying pressurized air to the single bank of air orifices. PA1 the Dupre system is not capable of producing quality snow at freezing temperatures milder than -6.degree. C. using a water volume that would be commercially viable. The literature indicates that the system can only operate at -6.degree. C. with a low humidity of about 60%. There are many ski areas that have a significant number of days during the season when the temperature is milder than -6.degree. C. There is therefore a need to develop a system which can operate at milder freezing temperatures; PA1 it is always desirable to increase the snow-making capacity of the snow gun; PA1 there is a need to provide a snow gun which can be used without air when the temperature is cold; and PA1 there is a need to provide a flanged snow gun that is disconnectable from the tower, for easy removal to permit service to the snow gun and to permit replacement with a snow gun having upgraded components. PA1 improved atomization, which leads to finer droplet size and the ability to nucleate and form snow at freezing temperatures milder than -6.degree. C.; PA1 more complete atomization, as the entire width of the water spray preferably is contacted by the air jet; PA1 increased snow-making capacity, as more water banks can now be incorporated into a single snow gun and their sprays can be independently nucleated; PA1 versatility, in that nozzles of different capacity can be used in a coupled pair and the nature of the fluid discharge of these nozzles can be switched from ground; and PA1 the option to terminate air supply during cold weather conditions.
In a subsequent U.S. Pat., No. 3,822,825 issued Jul. 9, 1974, Dupre taught bringing the water and air separately up the tower in inner and outer, concentric, spaced apart conduits. The air flowed through the inner conduit passageway and the water through the outer annular passageway formed between the conduits. As a result, the water stream functioned to insulate the air stream. There is moisture in the air and it will condense and freeze to form "rime ice" if the atmospheric temperature is low enough and the air stream becomes chilled sufficiently. In another aspect taught, the air was delivered to a tee and released into the atmosphere through a pair of diametrically opposed orifices. These orifices were holes drilled through the wall of the outer conduit, to communicate with the bore of the tee. Dupre taught that the air outlet should be flush with the outer surface of the outer conduit, to avoid cooling of the air while passing through the orifice with consequent formation of rime ice, which could block the orifice. Dupre further taught discharging the water through a nozzle angled at 45.degree. relative to the long axis of the conduit and having a shaped orifice adapted to deliver a substantially flat and V-shaped spray. His air orifice was positioned just above the water nozzle and was angled at about 90.degree. relative to the long axis of the conduit. The term "associated pair" is used herein to denote a pair of outlets arranged so that the air jet and water spray which they produce intersect with the result that the air atomizes the water and a nucleated plume is produced. The air orifice was positioned to discharge its jet into the throat of the water spray. In another feature, Dupre taught mounting diametrically opposed associated pairs of air orifices and water nozzles, each pair being at a common elevation. This arrangement is referred to as providing a "bank" of associated pairs of air orifices and water nozzles. Inherent in this design were the following concepts:
In a still more recent patent, U.S. Pat. No. 5,004,151 issued Apr. 2, 1991, Dupre addressed the need to increase snow production capacity. A discrete snow gun was attached to the upper end of a conduit tower secured to a vertical post. The snow gun had an associated pair of water and air outlets, comprising a water nozzle and an air orifice. A second water nozzle was inwardly spaced along the gun from the outer water nozzle of the associated pair. The second water nozzle was inclined at a more acute angle than the first water nozzle, so that the water spray of the second nozzle would converge into and contact the plume produced by the associated pair. In this way, the available single jet of air was used to atomize the two sprays of water.
The Dupre system has won commercial success. The commercial version incorporates the features described above. It can be described more specifically as follows:
While the Dupre system has been an admirable success, there are still certain shortcomings which could be improved upon. More particularly:
It is an objective of the present invention to provide a snow gun which satisfies these needs.
By way of further background, it is pointed out that the V-jet nozzles used in the art are classified by the designations 5020, 5040 and 5060. A 5020 nozzle produces a flat, V-shaped spray having an angularity of about 50.degree. and discharges 2 U.S. gpm of water, when operated at 40 psi. A 5040 nozzle produces a similar spray at 4 U.S. gpm at 40 psi. And the 5060 nozzle produces a similar spray at 6 U.S. gpm at 40 psi. If the pressure is increased, all of the nozzles will deliver more water at a wider angle.